Filter bypass switches are commonly used to monitor the condition of the oil filter or oil filter screen and to provide a warning to the operator when the oil filter becomes clogged or otherwise restricted. A typical oil filter housing group or arrangement includes a filter housing, an oil filter, a spring biased spool and a filter bypass switch, the filter bypass switch including a plunger which is disposed in a housing and adapted to reciprocate therein, and including a pair of screw terminals. When the oil filter is clean, the plunger associated with bypass switch is urged into a closed position by the spring loaded spool, one end portion of the plunger thus making contact with the pair of screw terminals and closing the switch formed by the screw terminals and the one end portion of the plunger. As sludge or dirty oil builds up and the filter becomes dirty or clogged, a differential pressure moves the spring loaded spool in the opposite direction away from the switch plunger and a second spring, the second spring being adapted to normally urge the plunger away from the screw terminals. The differential pressure moves the plunger out of electrical contact with the screw terminals thus opening the circuit between the one end portion of the plunger and the pair of screw terminals. When the filter bypass switch is open, the operator is provided with a warning that the filter is restricted or clogged.
With this type of filter bypass construction, movement of the plunger in and out of contact with the screw terminals as well as the force of the spring loaded spool pushing the plunger back into contact with the screw terminals may cause denting and/or other damage to the screw terminals as well as to the plunger contact surface, thereby causing intermittent electrical contact even when the plunger is in its closed position. Also, with this type of construction, the plunger contact surface and the screw terminal surfaces may become coated with a thin layer of contamination which may also cause an intermittent electrical condition. Still further, due to the particular construction of the screw terminals, oil leakage past the screw terminals may also occur.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.